The hormone, human chorionic gonadotropin, hCG is produced during pregnancy. It is made by cells that form the placenta which nourishes the egg after it has been fertilized and becomes attached to the uterine wall. The hCG can be first detected by a normal blood test about 11 days after conception or about 12-14 days after conception with a urine test. In general the hCG level will double every 72 hours. The hCG level will reach its peak in 8 to 11 weeks of the pregnancy and then will decline and level off for the remainder of the pregnancy.
Table 1 shows the Gestational age of the nourished egg after LMP as being proportional to levels of hCG in blood or urine.
TABLE 1hCG level of UrineGestational age after LMP<5.0mIU/mlNon pregnancy5-50mIU/ml3weeks5-426mIU/ml4weeks18-7,340mIU/ml5weeks1,080-56,500mIU/ml6weeks7,650-229,000mIU/ml7-8weeks25,700-288,000mIU/ml9-12weeks13,300-254,000mIU/ml13-16weeks4,060-165,400mIU/ml17-24weeks3,640-117,000mIU/ml25-40weeks
Accordingly, the levels of hCG detected can be used as an aid to determine a fetus's gestational age and status at various stages of a pregnancy. For examples, a low hCG level could indicate possible miscarriage, blighted ovum, or ectopic pregnancy. A high level of hCG may indicate molar or multiple pregnancy.
There are many brands of pregnancy test kits commercially available, however they only provide a single answer (Yes or No) as to whether a specific level of hCG is reached. No additional information is provided regarding the various concentration levels of the hCG being detected. Clinician often use hCG level information in order to monitor the course of pregnancy, however currently there is a lack of convenient, inexpensive, point care technology and product available.
For example, in order determine the levels of hCG, one must be subjected to a standard lab test which utilizes ELISA hCG test by using a women's blood specimen. Although the results do show acute concentration of hCG as mIU/ml in blood, the procedure is involved and requires an invasive blood specimen collection procedure. To obtain the hCG concentration results, the blood is often transferred to a specialized laboratory where a laboratory technician performs the necessary tests. The laboratory is typically away from the clinic where women's blood specimen was taken. The ELISA hCG test takes about an hour to perform the test but there is the additional time for the hCG test results to be delivered back to a physician's clinic. Accordingly, to receive the results of a hCG test, there is usually a minimum one day turnaround. Another drawback is the cost of performing the hCG test at the specialized laboratory which requires additional labor and materials.
Gestational age can also be determined using a transvaginal ultrasound examination. The ultrasound examination enables a clinician to visualize at least a gestational sac once the hCG levels have reached between 1,000-2,000 mIU/ml which is in about 5 weeks into a pregnancy. However, ultrasound technology cannot detect the status of early stages of pregnancy which is an essential time to watch for possible health or abnormal courses of pregnancy.
There is a commercial test available for detecting hCG levels of 2000 mIU/ml or greater. The test is a Wampole immunochemical latex agglutination slide test. Clinicians utilize this product to monitor a large fluctuation in hCG levels in pregnant women after a miscarriage or a procedure when the hCG levels are supposed to drop substantially. Accordingly, there is much variation in the sensitivity of the Wampole slide test. Moreover, the latex agglutination process of the Wampole slide—based on latex agglutination process, its sensitivity can vary from 1000 mIU/ml or 3000 mIU/ml. Since the Wampole slide test is for detecting high hCG levels, it only provides a single level of hCG with no semi-quantitative information. In view of the shortcomings of current tests for hCG levels, there is a need for a simple to use, less evasive, inexpensive, accurate, hCG level tester that overcomes the disadvantages of current practices.